Purified hydrogen gas is used in the manufacture of many products including metals, edible fats and oils, and semiconductors and microelectronics. Purified hydrogen gas also is an important fuel source for many energy conservation devices. For example, fuel cells use purified hydrogen gas and an oxidant to produce electrical potential. Various processes and devices may be used to produce hydrogen gas. However, many hydrogen-producing processes produce an impure hydrogen gas stream, which may also be referred to as a mixed gas stream that contains hydrogen gas and other gases. Prior to delivering this stream to a fuel cell stack or other hydrogen-consuming device, the mixed gas stream may be purified, such as to remove at least a portion of the other gases.
A suitable mechanism for increasing the hydrogen purity of the mixed gas stream is to utilize at least one hydrogen-selective membrane to separate the mixed gas stream into a product stream and a byproduct stream. The product stream contains a greater concentration of hydrogen gas and/or a reduced concentration of one or more of the other gases than the mixed gas stream. The byproduct stream contains at least a substantial portion of one or more of the other gases from the mixed gas stream. Hydrogen purification using one or more hydrogen-selective membranes is a pressure driven separation process, in which the one or more hydrogen-selective membranes are contained in a pressure vessel. The mixed gas stream contacts the mixed gas surface of the membrane(s), and the product stream is formed from at least a portion of the mixed gas stream that permeates through the membrane(s). The byproduct stream is formed from at least a portion of the mixed gas stream that does not permeate through the membrane(s). The pressure vessel is typically sealed to prevent gases from entering or leaving the pressure vessel except through defined inlet and outlet ports or conduits.